1. Field of the Invention
The present invention relates to a compound imaging lens including three lens elements.
2. Description of the Related Art
In recent years, the advancement of miniature solid-state image sensors for mobile cameras mounted in applications such as mobile phones has resulted in the use of solid-state image sensors having pixels 3 μm or smaller in size. An imaging lens having three or more lens elements is necessary to practically accommodate solid-state image sensors of such extremely small pixel sizes. Such optical systems require corrections to sufficiently compensate for various aberrations.
Unexamined Japanese Patent Application KOKAI Publication No. 2006-308789 discusses a known example of an imaging device using three lens elements.
However, the imaging lens discussed in the Unexamined Japanese Patent Application KOKAI Publication recited above has a small depth of focus, causing difficulties when focusing. Moreover, such an optical system is highly sensitive to errors.
The present invention was accomplished in consideration of the problems recited above, and is directed to provide a compound imaging lens that has three lens elements, a compact size, a large depth of focus, and low sensitivity to error.